1. Field of the Invention
The present invention relates to a liquid crystal display device and a manufacturing method thereof, and particularly to a liquid crystal display device and a manufacturing method thereof for coating a substrate with a sealing material by using a dispenser.
2. Description of the Related Art
Liquid crystal display devices have been adopted as display devices with various sizes, raging from small-sized portable phones to large-sized TVs. A liquid crystal display panel of the liquid crystal display device includes a first substrate, a second substrate, a sealing material through which the first substrate and the second substrate are stuck together, and a liquid crystal enclosed inside a liquid crystal enclosure area encircled by the first substrate, the second substrate, and the sealing material.
Methods of forming a sealing material include a method of coating by using a dispenser and a method in which the sealing material is formed by printing, such as screen printing. Further, methods of enclosing a liquid crystal include a method in which a liquid crystal enclosure port is provided at a part of the sealing material to inject a liquid crystal from the liquid crystal enclosure port, and the liquid crystal enclosure port is sealed with an end-sealing material. Other methods include a liquid crystal dropping-enclosure method in which the sealing material is formed in a ring shape (for example, a rectangular shape) with the whole circumference closed without providing the liquid crystal enclosure port in the sealing material so as to drop a liquid crystal into the inside of the ring portion, and then the first substrate and the second substrate are stuck together for enclosure. Moreover, in the case of manufacturing the liquid crystal display panels, there is performed a gang printing in which plural liquid crystal display panels are formed by arranging on a mother substrate, and the mother substrate is cut so as to be separated into individual liquid crystal display panels.
FIG. 9 is a plan view explaining an example of a coating pattern of the sealing materials by using a conventional dispenser. In FIG. 9, by allowing the dispenser to move along a track TR, the ring portion configured by a sealing material SL4 and an extension portion configured by a sealing material SL5 are formed without stopping the discharge of the sealing material. At a portion of the sealing material SL5, the dispenser reciprocates, but a center position of a seal width is displaced from another one for drawing. Then, a liquid crystal is dropped into a liquid crystal enclosure area LCA encircled by the ring portion.
FIG. 10 is a plan view explaining another example of a coating pattern of the sealing materials by using the conventional dispenser. Such a pattern is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2006-184381. In FIG. 10, the substrate is coated with a sealing material SL1 having a seal width W3 while allowing the dispenser to move along a track TR1. Next, the substrate is coated with a sealing material SL2 having a seal width W4 while allowing the dispenser to meander along tracks TR2 to TR10. Thereafter, a crystal liquid is dropped and the substrates are stuck together. FIG. 10 shows a case in which two ring portions are formed for a gang printing.
FIG. 11 is a plan view explaining a case in which the substrates are stuck together by using the sealing materials in FIG. 10. In a state where the substrates are stuck together, the sealing materials SL1 and SL2 are squeezed and spread. As a result, the seal width W2>W4 is satisfied in the ring portion, and the seal width W1>W3 is satisfied in the extension portions other than the ring portion. In addition, since the substrate is coated with the sealing materials SL1 and SL2 in parallel in the extension portions, W1>W2 is satisfied. Thereafter the substrates are cut at a cutting line CTL.
However, in the pattern shown in FIG. 9, there is formed an unnecessary portion on the substrate by a distance d of the extension portion of the sealing material SL5.
In the case of the patterns shown in FIGS. 10 and 11, the unnecessary area with the distance d as shown in FIG. 9 is not generated when two-dimensionally arranging the ring portions in the gang printing. However, as shown in FIG. 11, the seal width W1 at the cutting line CTL increases, and thus there is a possibility that defects are generated at the time of cutting.
FIG. 12 is a plan view explaining still another example of a coating pattern of the sealing materials by using the conventional dispenser. FIG. 13 is a cross sectional view in FIG. 12. FIG. 13 illustrates portions of the tracks TR5 to TR7 in FIG. 12, and shows a state in which the dispenser is moved in the mid-course of the track TR7. FIG. 14 is a plan view explaining a case in which the substrates are stuck together by using the sealing materials in FIG. 12.
FIG. 12 is different from FIG. 10 in that double-drawing areas DDs of the sealing materials are provided at portions of the tracks TR2, TR6, and TR10. In this case, as shown in FIG. 13, a gap g ranging from a surface of a mother substrate MSUB1 to a dispenser DSP is as high as twice, or more, a height h ranging from a surface of the mother substrate MSUB1 to an upper face of the sealing material SL1 with which the substrate is already coated. Accordingly, the sealing material SL2 is overlappingly coated on the sealing material SL1 at the double-drawing areas DDs. As a result, as shown in FIG. 14, the seal width W1 at the cutting line CTL increases, and thus there is a possibility that defects are generated at the time of cutting, as similar to the case of FIG. 11.
Objects other than the above-described objects become apparent from the description of the whole specification and the drawings.
In the liquid crystal display device according the present invention, a relation between the seal width W1 at the cut-end portion of the substrates and the seal width W2 of the ring portion is represented as W2≦W1≦1.2W2.
In the manufacturing method of a liquid crystal display device according to the present invention, when the dispenser passes over the sealing material with which the substrate is already coated, the dispenser passes over the same in a state where a seal discharge amount per unit length is smaller than that with which the dispenser passes for the first time. It is desirable that the dispenser satisfy 0.8h≦g≦1.2h where g represents a gap ranging from a surface of the first substrate to the dispenser and h represents a height ranging from a surface of the first substrate to an upper face of the sealing material with which the first substrate is already coated.